Julie Schenecker, 50, a military officer's wife, was arrested Friday when police, responding to call from a concerned relative, found her covered in blood on the back porch of her home.

The woman allegedly confessed to the officers there that she had shot her 13-year-old son and then her 16-year-old daughter because they were "mouthy."

According to police, Schenecker shot her son in the face while they were on the way to soccer practice, then drove to the family home in in a gated country club community in north Tampa, where she shot her daughter in the back of the head while the teen was studying at her computer.

"I think we will never understand how or why a mother could take the lives of her children," police spokeswoman Laura McElroy said. "That was the only reason she provided to our detectives."

Schenecker's daughter, Calyx, 16, was found in an upstairs bedroom, and Beau, 13, was found in an SUV in the garage, McElroy said.

Both had been shot with a .38-caliber pistol that police believe had been bought five days earlier, according to the Tampa Tribune.

Investigators believe the teens "never saw it coming," McElroy said.

Schenecker, who was charged with two counts of first-degree murder, was taken to Tampa General Hospital just before midnight, ABC affiliate WFTS-TV in Tampa reported.

Hillsborough County Sheriff's officials said she is being treated in the ICU for a previous medical condition, according to WFTS-TV.

Police said they went to Schenecker's home Friday morning after receiving a call from the woman's mother, who called from Texas saying she had been unable to reach her daughter. She told police Schenecker had been depressed and complained about her children, WFTS-TV reported.

After the woman allegedly told them what she had done, McElroy said, officers found a note she had written saying she planned to kill her children and then herself.

The motive she allegedly gave, both in the note and in her interviews with police, was the children "talked back and were mouthy," McElroy said.

"During a post-Miranda interview with detectives, the suspect confessed to killing her two children," police said in a statement. "She described the crimes in detail."

According to WFTS-TV, Schenecker's husband, Army Col. Parker Schenecker, is stationed at the headquarters of U.S. Central Command at MacDill Air Force Base in Tampa.

CentCom spokesman Lt. Col. Michael Lawhorn told the station that Parker Schenecker, a career Army intelligence officer, had been away for several days. Police said they had contacted the husband in Qatar Friday and told him his children had been killed.

"They seemed like a nice family," said Charanun Soodjinda, 38, who lives across the cul de sac from the Scheneckers. "I never thought this would happen. How could you do that to your children?"